Condensed Pyridazines. VII

The reaction of 7-(methylsulfonyl)- and 7-chloro-1-penyl-1H-imidazo[4, 5-d]pyridazines (1 and 2) with active methylene compounds (5a-d) or ketones (5e-g) in the presence of sodium hydrige gave the corresponding 7-substituted imidazopyridazines (6a-g). A similar substitution of both 1 and 2 with methoxide ion (8) gave the 7-methoxy-imidazopyridazine (9). However, 1 and 2 reacted with BuNH2 (10) in a different way from the above substitution, resulting in the formation of the corresponding ring fission products of the imidazole portion, 3-substituted 5-amino-4-anilinopyridazines (11 and 12, respectively). The reaction of 1 with alkylmagnesium halides (13a-d) gave the 4, 5- and 2, 3-adducts (III and IV) which were converted into the corresponding 4-alkyl- and 2-alkyl-imidazopyridazines (14a-d and 15a, b) by potassium ferricyanide oxidation. A [4+2] cycloaddition occurred in the reaction of 1 with 1-piperidinocyclopentene (16a) to give the tetrahydroindeno[5, 6-d]imidazoles 17 and 18.